Complete vs Incomplete Proteins

When you hear the phrase complete vs. incomplete protein, it’s simply referring to a foods amino acid profile. Most people know, that protein plays a critical role, in building and rebuilding lean muscle mass through the process of protein synthesis. However, far less is known in regards to the variety of different proteins and the potential benefits of consuming complete vs. incomplete proteins. 

In this article, we’re going to cover the following

  1. What Are Complete Proteins?
  2. What Are Incomplete Proteins?
  3. What Is A Complementary Protein?
  4. Is Soy A Complete Source Of Protein?
  5. Is Collagen A Complete Protein?

What Are Complete Proteins?

A complete source of protein is a protein that contains all of the essential amino acids. Complete proteins are derived mostly from animal sources such as

  • Pork
  • Poultry
  • Beef
  • Turkey
  • Shrimp
  • Lamb
  • Fish
  • Dairy (Whey, Cheese, Milk, Yogurt)

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There are 21 amino acids that are utilized for human growth and metabolism. Twelve of these amino acids are considered to be nonessential, meaning that they can be synthesized by your body and do not need to be acquired through your diet. The remaining nine amino acids (methionine, lysine, isoleucine, histidine, valine, tryptophan, threonine, phenylalanine and leucine.) are essential and need to be consumed through dietary sources of protein. The absence of these essential amino acids will inhibit the ability of tissue growth and repair, therefore limiting your capacity to build and rebuild lean muscle mass [R].

Complete vs incomplete protein

What Are Incomplete Proteins? 

Incomplete proteins are those found in vegetables such as beans, legumes, nuts, and tofu and will generally lack one or more of the essential amino acids. 

If you’re vegan and/or vegetarian, it’s important that you eat a variety of different foods, in order to derive all of the essential amino acids through incomplete protein sources. Combining incomplete protein sources do provide a good nutritional profile to build lean muscle mass. However eating a non-varied diet, with limited protein sources, can result in a limited capacity to build and rebuild lean muscle mass, as compared to consuming animal-based protein sources [R].

RELATED ARTICLE The Best Muscle Building Foods For Plant-Based Diets

Vegetable Sources that are considered to be complete sources of protein include but are not limited to 

  • Edamame (Soy)
  • Quinoa
  • Chia Seeds
  • Hemp
  • Amaranth
  • Spirulina

RELATED ARTICLE Spirulina: A Miracle From The Sea Or Just Pond Scum?

Vegetable sources that are considered to be incomplete sources of protein include but are not limited to

  • Legumes (which are the richest source of plant-based protein Lentils, split peas, black-eyed peas) [R].
  • Beans (black, kidney, garbanzo, lima, navy, pinto, white, kidney)
  • Nuts (almonds, cashews, hazelnuts, pecans, pistachios, and walnuts)
  • Rice
  • Wheat
  • Seeds (pumpkin seeds, sesame seeds, and sunflower seeds)
  • Nut Butters (Peanut, Macadamia, Cashew, Almond) 

RELATED ARTICLE Nut Butters: Are They All That They’re Cracked Up To Be? 

Some sources of protein are considered to be inferior since they do not contain all of the essential amino acids. It’s important to combine incomplete proteins, in order to derive all of the essential amino acids you need for optimal metabolic function. 

Complete vs incomplete proteins

What Are Complementary Proteins?

When incomplete proteins are combined, they often make what’s called a complementary protein, (a complete protein from two or more sources). 

Some proteins are inferior to others, while others provide higher quality content with more vitamins and minerals. That being said, it’s important to know the difference between complete and incomplete proteins, so that know which type of protein will give you the greatest benefit.

Is Soy A Complete Source Of Protein? 

Despite being classified as a legume, soybeans provide a complete source of protein, since they contain all of the essential amino acids. One benefit of soy protein vs complete animal protein sources is that soy has been shown to lower cholesterol [R].

RELATED ARTICLE The Shocking Truth About Soy

Is Collagen A Complete Protein? 

Collagen is a very unique type of protein and contains an amino acid profile, that is very often lacking in modern day diets, which includes glycine, proline, alanine, and hydroxyproline. Yet, despite its uniqueness, Collagen is not considered a complete source of protein. However, Collagen does provide an immense amount of health benefits in regards to skin, hair, nails, joints, bones, and let’s not forget the potential athletic benefits such as building lean muscle mass and optimizing recovery.3

RELATED ARTICLE The Complete Guide To Collagen Protein: Uses & Benefits

Complete Vs. Incomplete Proteins: Takeaway

When it comes to complete vs. incomplete proteins, it's important that you get complete sources of protein, so that you derive all essential amino acids to help build and rebuild lean muscle mass. Whether it's from creating a complementary protein by adding different protein sources together, animal-based based protein, the quality of the protein you eat truly does matter. 

Looking for the best complete source of protein?

Whey Protein Isolates are the purest protein source available. Whey protein isolates contain protein concentrations of 90% or higher. During the processing of whey protein isolate there is a significant removal of fat and lactose, making it a great option for those that are lactose intolerant, or who want the purest form of protein


  1. Hoffman, Jay R., and Michael J. Falvo. “Protein – Which Is Best?” Journal of Sports Science & Medicine3 (2004): 118–130. Print.
  2. Michelfelder AJ. Soy: a complete source of protein. Am Fam Physician. 2009;79(1):43-7.
  3. Zdzieblik, Denise et al. “Collagen Peptide Supplementation in Combination with Resistance Training Improves Body Composition and Increases Muscle Strength in Elderly Sarcopenic Men: A Randomised Controlled Trial.” The British Journal of Nutrition 114.8 (2015): 1237–1245. PMC. Web. 9 Oct. 2018.
  4. Harvard Health Publishing. “Getting Your Protein from Plants - Harvard Health.” Harvard Health Blog,



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